Generally, a socket for ICs (Integrated Circuits) is loaded in a test board or a burn-in board. The socket is connected to measuring devices for measuring the properties of a burn-in chamber or peripheral devices and an IC, thus being used in a system for testing a series of ICs. In this case, the burn-in chamber is used to input and output power and an electric signal, which are required to drive the IC, through an I/O terminal (input and output terminal) formed on the board (test board, burn-in board).
Among the ICs that have been widely used, a BGA (Ball Grid Array) type of IC is shaped as shown in FIGS. 1 and 2. Terminals of the IC, that is, balls, are arranged throughout the bottom of the IC, thus dramatically reducing the size and thickness of the IC.
Generally, the pitch between the balls of the BGA-type IC is 0.5 D, 0.75 D, 0.8 D, 1.0 D, 1.27 D, 1.6 D, etc. Each ball has a diameter from 0.3 D to 0.9 D. The height from the lower surface of the BGA-type IC to each ball is set to 0.2 D to 0.6 D. As the pitch between the balls is reduced, the diameter and height of the ball is reduced.
Meanwhile, as shown in FIGS. 3 and 4, an LGA-type IC is an IC which removes balls from the BGA-type IC. A socket for loading the LGA-type IC is provided with a plurality of contacts having a predetermined elastic force in a vertical direction. The lower terminal of each contact is connected to a PCB (Printed Circuit Board).
In this case, the upper terminal of each contact is formed to contact the land of the LGA-type IC which is loaded in the socket. Thus, a device for pressing down the LGA-type IC so as to provide stable electrical contact must be provided on the socket.
When a physical force acting on the LGA-type IC by the pressing device is divided by the number of contacts, a physical force applied to one contact is calculated. The physical force applied to the contacts is about 15 gf per contact. Assuming that the LGA-type IC has 1000 lands, strong physical force of about 15Kgf is required.
Thus, the socket in which the LGA-type IC is loaded must be provided with a latch so as to efficiently apply strong physical force to the IC. The socket must be also provided with reliable contacts which may stably transmit additional power or signals.
A conventional representative socket for loading an LGA-type IC is provided with contacts 16 which are bent in an arc shape, as shown in FIGS. 5 and 6. Further, the socket is provided with a lever 13 which presses the LGA-type IC with a strong physical force. The contacts 16 are elastically deformed downwards by the lever 13.
As described above, the conventional socket for the LGA-type IC is problematic in that the contacts are arranged and assembled using additional parts for assembling the contacts having the arc-shaped bent parts, so that a greater number of components is required, assembly is difficult, and the lever for applying strong physical force and the socket for operating the lever have complicated constructions. The conventional socket has another problem in that the cost thereof is increased and the quality thereof is deteriorated due to the complicated construction of the socket.